Method of making heat exchange tubes



Filed Sept. 12, 1942 INVENTOR. WV/7K0 66 W41 Z1462 ATTORNEY Patented Dec. 26, 1944 UNITED STATES PATENT OFFICE Edward E. Wallace, Detroit, Mich, asslgnor to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application September '12. 1942, st ains; 458,096

which may be made of wax, metal which melts This invention relates to methods of making heat exchange tubes or conduits which have heat exchange projections on the inside of the tube. Tubes of this character are diflicult to produce in commercial quantities and as far as I am aware tubes having irregular shapes and inside projections or heat exchange elements havenot been made.

The primary object of the present invention is to provide an improved and economical method of making heat exchange conduits or tubes having numerous projections inside the tube which greatly increases the interior surface area so as to cause a high thermal transfer coefllcient to exist between the projections and their tubular container.

Another objectis to provide a method whereby a heat exchange tube having the above mentioned internal projections can be I readily formed of irregular contour.

Other objects and advantages of the present invention will be apparent from the following description and. the accompanying drawing, in

Fig. 1 is a perspective view of a heat exchange tube embodying the invention,

Fig. 2 is a perspective view of a core in an intermediate stage of the manufacture of the tube shown in Fig. 1, according to one method embodying the invention,

Fig. 3 is a longitudinal section of the core shown in Fig. 2 with a completed heat exchange tube formed on it,

Fig. 4 is a perspective view, partly broken away,

showing atube and core made by another methtact of high eiiectiveness. The wires are preferably embedded in the wall of the tube, providin: joints of great mechanical strength.

The invention includes methods of conveniently and economically making such atube. One such method is shown in Figs. 1 and 3. A large number of staples, each including a pair -of pins or filaments I! connected by a connecting end portion ll, are driven into a suitable core ll.

'ical connection.

at a relatively low temperature such as lead, or any other suitable substance which can readily be removed from the completed tube. Prefer- .ably the U-ends l4 project slightly from the electrolytically deposited metal forms an intimate contact with the connecting ends of the pins and adheres firmly to them. If the connecting ends of the pins are not in too close contact with the core, the electrolytically deposited metal forms about them' so that in the completed heat ex change tube the pins are embedded in the wall of the tube and integral withthe metal of the wall. This forms agood thermal and mechan- The filaments themselves, being embedded in the core receive no deposit of metal, and thus do not build up or increase in thickness. After the tube has been formed asdescribed the core is removed. In the case .of

metal or wax cores, this is done simply by melting out the core.

I Fig. 4 illustrates a tube made by another method involving the invention. Card cloth is first formed about any suitable core such as a paper tube 20 of streamlined cross-section. Card cloth i a commercially available article consisting of a fabric backing or support It through which are driven a large number of small staples 22 which provid a large number of closely spaced pins 23 projecting from one face of the fabric. The back of the fabric is then "coated with graphite and immersed in the electrolyte so that the tube 24 is. electrolytically deposited on the fabric and staples. If necessary theprojecting pins are coated with any suitable stop varnish to prevent their receiving a deposit of metal. It is important that the conducting support for the staples be immersed in the electrolyte, as opposed to merely dipping the ends of the staples into the electrolyte, in order that the electrolytically deposited tube may be built up on the conducting support and on the staples at the same time. This produces an intimate thermal and mechanical bond, and a tube which is strong mechanically and capable of withstanding high pressure.

After the tube 24 has been deposited to the desired thickness, the form 20 and backing 2| are removed by any suitable method, such as by burning or dissolving out, leaving the tube with the pins embedded in its wall and projecting from its interior surface.

Having thus described my invention, what I- claim and desire to protect by Letters Patent is: The method of making a heat exchange tube 

